Spark-knock, otherwise known as detonation or auto-ignition, is a detrimental phenomenon that can occur in a cylinder of a spark-ignition internal combustion engine of the type generally used in motor vehicles. Spark-knock occurs when fuel inside the cylinder combustion chamber is prematurely detonated as a result of rapid temperature and pressure rise due to combined compression by the piston and the ignition by a spark plug of the inlet fuel-air charge. Consequences of spark-knock can be loss of power, degradation in engine durability, and/or an increase in undesirable exhaust emissions.
One approach for minimizing spark-knock in the automotive industry is to vary the engine's spark timing. A knock-sensor, a type of accelerometer located on the engine block, is configured to detect knock-induced engine block vibrations, and is then used to generate a signal to the engine computer to retard ignition timing. The net effect of this approach is that while knock is minimized or eliminated, retarding of spark can also have an undesirable impact on the engine's power and overall efficiency during the affected operating cycle.
Another approach for combating spark-knock is to reduce an engine's static compression ratio. While reducing the compression ratio dispenses with the need for a knock-sensor, such an approach can reduce engine power and overall efficiency under all operating conditions.
In view of the above, it is therefore apparent that an efficient method of eliminating spark-knock in spark-ignition internal combustion engines while retaining full engine performance under most operating conditions would be most beneficial.